The present invention relates to an apparatus for detecting an approaching conductor, an apparatus for detecting a an approach point of a conductor, and an electrostatic capacity type touch panel apparatus, and more specifically, to an apparatuses for detecting an approaching conductor and an approach point of a conductor, in which a position of a detected conductor is detected in accordance with an electrostatic coupling capacity generated between the detected conductor and a resistive membrane, and an electrostatic capacity type touch panel apparatus in which a state of a touching finger on a panel is detected by use of an electrostatic capacity between the finger and the panel.
A conventional apparatus for detecting a position of a conductor is disclosed in Japanese Patent No. 1,536,723, for example, in which four corners of a resistive panel is voltage-driven by an operational amplifier, while a drive current is detected by a differential amplifier. Further, Japanese Patent Nos. 1,754,522 and 2,037,747 disclose an example in which detects a change in capacitance of a lattice-like conductor of a panel including a coupling capacity with a finger. Further, Japanese Patent No. 2,603,986 discloses an example which detects an impedance of a resistive panel including a coupling capacity with a finger. As another example, there is a finger-position detecting apparatus disclosed in Japanese Patent No. 1,881,208 in which four points of a touch panel is AC voltage-driven by a transformer, while a drive current component is applied to a differential amplifier.
The above-mentioned prior arts were based on an idea in which an electric signal is applied from a sensor panel into a detected conductor such as the human body. As a result, since a construction of their circuit was designed by use of complicated means, signals were not suitably processed. Furthermore, there was uncertainty (obscurity) why a false earth was caused by a detected conductor. Therefore, there was potential state which bring about an unstable detection.
Additionally, for electrostatic capacity type touch panel apparatuses in which AC signal is applied into a finger for detection of the approaching finger, in which an approaching finger is detected, which designates one section on the panel by means of a finger, and which indicates one point on the panel by means of a finger for inputting coordinates, the used signal frequencies were 200 kHz or less because of easy production of the apparatus.
However, also in the instance, there was a potential problem which bring about an uncertain detection, since the reason why a human body is grounded, was unstable (obscure) state.
Considering problems described-above, the present invention is to provide an apparatus for detecting an approaching conductor, an apparatus for detecting an approach point of a conductor, and the apparatus has a voltage-oscillating system which includes a sensor panel or a sensor conductor array, a shield panel, a signal processing circuit, a ground circuit and a power circuit such that a conductor such as a human body undergoes an electrostatic coupling, and thereby equivalently receives an electric oscillation (AC signal) so as to be processed as a signal to ground, and resultant processing output is then transmitted to a non-oscillating system through an isolator, the conductor belonging to the non-oscillating system (including resistors which enables an adequate flow of a stable oscillation).
Furthermore, oscillation frequency is set to over 200 kHz so that signals are unconditionally detected in a stable state. According to the present application, a term xe2x80x9ca position of an approaching conductorxe2x80x9d means a position where is about 1 m to 2 cm from the apparatus, and a term xe2x80x9capproach point of a conductorxe2x80x9d means a point where is in about 5 cm to 0 cm (contacting) from apparatus.
From the viewpoint, observation, or measurement of the voltage-oscillating system, it seems that voltage oscillation generated from the detected conductor belonging to the non-vibrating system is measured. In the present apparatus, the measurement of an electric oscillation (AC signal) is made, when AC signal is equivalently received by the sensor panel or sensor through an electrostatic coupling between a detected conductor and resistant membrane. In other words, it can be said to be the electric system which corresponds to the Ptolemaic system. This differs from the conventional processing of signals in which signals are applied into a finger of a human body as a conductor. According to the present invention, the received signals to ground can be processed by the voltage-oscillating system, and various designs of the circuit are then allowed. An input of low impedance effects easily considerable elimination of a bed influence of a floating capacity.
Furthermore, when a voltage oscillation is generated from the conductor such as a human body, lower electromagnetic wave is radiated due to the antenna effect of the human body. Generally, the radiant impedance of the antenna would be reduced, if higher oscillation frequency had been set. The conductor such as a human body undergoes a load of the radiant impedance. Therefore, even though the human body or operator is sitting on a chair or standing on a stand, the voltage oscillation is effectively suppressed in response to the oscillation frequency of over 200 kHz.
The present invention is concerned with neither of the apparatuses in which a measurement of impedance is made and in which a measurement of capacitance is made, but is directed to an apparatus for detecting an approaching conductor and/or an approach point of a conductor. The apparatus detects an approaching conductor and/or an approach point of a conductor in response to a level of a AC input signal of a voltage-oscillating system from the conductor such as a human body belonging to a non-oscillating system. In the apparatus, the false ground of the conductor is detected by use of the capacity to round, while the voltage oscillation undergoes suppression caused by a load due to the radiant impedance of the antenna. Therefore, even though the conductor having same size as a human body is at a distant position or point from the apparatus, the conductor can be detected in stable state.
The present invention is also directed to an electrostatic capacity type touch panel apparatus. In the apparatus, the false ground effect of the human body is not only performed by use of the capacity to ground, but also is performed by use of the voltage oscillation suppression effect caused by a load of the radiant impedance of the antenna. Therefore, even though a finger of the human body electrically floats on the apparatus, the finger is detected in stable state so that an AC signal can be applied into the finger.